This invention relates to external means for influencing electron beams within a color cathode ray tube and more particularly, to support means for exteriorly positioning and retaining a beam adjustment device on the neck portion of a color cathode ray tube.
Cathode ray tubes of the type conventionally employed in color television applications usually utilize several electron beams emitted from electron generating means oriented within the neck portion of the tube. These several beams are discretely directed to trasverse an apertured mask member and impinge a patterned cathodoluminescent screen spatially disposed therebeyond on the panel portion of the tube to effect a predetermined display of imagery thereon. For the beams to accurately converge and impinge discrete areas of the screen pattern in the desired manner, it is imperative that the individual beams be accurately controlled in their travel to the screen. External control of the respective electron beams is augmented by a beam adjustment device formed for positioning on the exterior surface of the neck portion of the tube envelope in the region of the electron gun structure. For example, one such control means, commonly referenced as a static convergence and purity device is conventionally comprised of a plurality of sequentially oriented annulate magnetic members and associated purity rings contiguously related in a manner to be individually rotatably adjustable on the neck portion of the tube.
One support means commonly utilized in the art for positioning and retaining these related magnetic members, embodied a cylindrical insulative sleeve having integral stop means formed thereon beyond which a clamp ring was positioned over tongue-like projections and tightened to hold the assembly upon the neck of the tube. In the assembled and positioned device, the annulate magnetic members and purity rings being positioned on the sleeve ahead of the stop means, were separately rotated to achieve the proper adjustment of the beams in the operating tube, whereupon a terminal threaded ring was tightened to collectively hold or lock the annulate members in proper adjusted positioning. This system was prone to a troublesome drawback evidenced in tightening of the terminal locking member. If the circumferential movement employed in securely tightening this member was greater than the holding power of the previously fastened clamp ring, the whole assembly was rotatably shifted on the neck portion of the tube. As a result, the complete adjustment procedure had to be repeated.